Oxide interface displaying electronically controllable ferromagnetism

Patent metadata

Field	Value
Publication number	US-11688539-B2
Application number	US-202117533044-A
Country	US
Kind code	B2
Filing date	Nov 22, 2021
Priority date	Jul 17, 2014
Publication date	Jun 27, 2023
Grant date	Jun 27, 2023

Abstract

A structure includes an electronically controllable ferromagnetic oxide structure that includes at least three layers. The first layer comprises STO. The second layer has a thickness of at least about 3 unit cells, said thickness being in a direction substantially perpendicular to the interface between the first and second layers. The third layer is in contact with either the first layer or the second layer or both, and is capable of altering the charge carrier density at the interface between the first layer and the second layer. The interface between the first and second layers is capable of exhibiting electronically controlled ferromagnetism.

First claim

What is claimed is:

1. A method of controlling an electronically controllable ferromagnetic oxide structure, the electronically controllable ferromagnetic oxide structure comprising:
(a) a first layer in contact with a second layer, wherein the second layer has a thickness of at least about 4 unit cells, the thickness being in a direction substantially perpendicular to an interface between the first and the second layers, wherein the interface is defined by a plane between the first and second layers; and
(b) at least one surface electrode and at least one interfacial contact, the at least one surface electrode and the at least one interfacial contact being in contact with at least one of the first layer or the second layer, wherein:
the at least one surface electrode and the at least one interfacial contact are configured to alter the charge carrier density at the interface between the first and second layers,
(ii) the at least one surface electrode is deposited on the second layer on a surface spaced from the interface, and the at least one interfacial contact extends from the surface spaced from the interface through the second layer to the interface, and
(iii) the interface between the first and the second layers is configured to exhibit electronically controlled ferromagnetism in response to alteration of the charge carrier density,

the method comprising:
(1) applying a positive voltage to the at least one surface electrode;
(2) applying a magnetic field to the electronically controllable ferromagnetic oxide structure; and
(3) switching the positive voltage applied to the at least one surface electrode to a negative voltage so as to cause the interface to switch between a ferromagnetic state and a non-ferromagnetic state.

2. The method of claim 1 , wherein the positive voltage and the magnetic field are applied simultaneously.

3. The method of claim 1 , wherein the positive voltage and the magnetic field are applied prior to a reduction in the charge carrier density at the interface.

4. The method of claim 1 , wherein the magnetic field is applied in a direction corresponding to a magnetic bit state defined according to a magnetic moment orientation of a ferromagnetic domain of the interface.

5. The method of claim 1 , wherein the first layer comprises SrTiO 3 and the second layer comprises at least one of LaAlO 3 , LaTiO 3 , EuTiO 3 , Al 2 O 3 , GaTiO 3 , or LaMnO 3 .

6. The method of claim 1 , wherein the interface comprises a TiO 2 -terminated SrTiO 3 surface.

7. The method of claim 1 , wherein the at least one surface electrode comprises at least one of Ti or Au.

8. The method of claim 1 , wherein the at least one interfacial contact is an arcuate contact disposed so as to be arranged concentrically around at least a portion of the at least one surface electrode.

9. The method of claim 1 , wherein the at least one surface electrode comprises a plurality of metallic circular top electrodes disposed in series.

10. The method of claim 1 , wherein the at least one surface electrode is grounded.

11. A method of altering a ferromagnetic state at an interface of a multi-layered oxide structure comprising at least a first layer and a second layer, the method comprising:
establishing a voltage difference between the interface and a material in contact with at least one of the layers of the multi-layered oxide structure, the interface being between the first and second layers of the oxide structure and defined by a plane between the first and second layers, wherein:
(a) the voltage difference is sufficient to alter a charge carrier density at the interface between the first and second layers of the oxide structure;
(b) the second layer has a thickness in a direction substantially perpendicular to the interface between the first and second layers;
(c) the oxide structure further comprises at least one surface electrode and at least one interfacial contact, the at least one surface electrode and the at least one interfacial contact being in contact with at least one of the first layer or the second layer, and
(d) the interface between the first and second layers of the oxide structure is capable of exhibiting electronically controlled ferromagnetism,

wherein the at least one surface electrode is deposited on the second layer on a surface spaced from the interface, and the at least one interfacial contact extends from the surface spaced from the interface through the second layer to the interface.

12. The method of claim 11 , wherein:
(a) the voltage difference is about 0.01 to about 15 volts; and
(b) the voltage applied to the material in contact with the at least one layer is greater than the voltage applied to the interface.

13. The method of claim 11 , wherein the interface comprises a TiO 2 -terminated [ 001 ] SrTiO 3 surface.

14. The method of claim 11 , wherein the first layer comprises SrTiO 3 and the second layer comprises at least one of LaAlO 3 , LaTiO 3 , EuTiO 3 , Al 2 O 3 , GaTiO 3 , or LaMnO 3 .

15. The method of claim 12 , wherein the at least one surface electrode comprises at least one of Ti or Au.

16. The method of claim 11 , wherein the at least one interfacial contact is an arcuate contact disposed so as to be arranged concentrically around at least a portion of the at least one surface electrode.

17. The method of claim 11 , further comprising grounding the at least one surface electrode.

18. The method of claim 11 , wherein establishing the voltage difference comprises:
(a) grounding the at least one surface electrode, and
(b) applying a voltage to the at least one interfacial contact so as to increase electron accumulation at the interface.

Assignees

• Univ Of Pittsburgh—Of The Commonwealth System Of Higher Education

Inventors

• Levy Jeremy
• Bi Feng
• Irvin Patrick R

Classifications

• H01F1/40

  of magnetic semiconductor materials, e.g. CdCr2S4 (devices using galvano-magnetic or similar effects H10N50/00) · CPC title

• G11C11/155

  with cylindrical configuration · CPC title

• H01F10/193

  Magnetic semiconductor compounds {(in general H01F1/40; multilayers, e.g. superlattices H01F10/3213)} · CPC title

• H01F10/3213

  Exchange coupling of magnetic semiconductor multilayers, e.g. MnSe/ZnSe superlattices · CPC title

• G11C11/161 Primary

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title